The First Class Mail letter (1 oz.) rate for postage purchased at the Post Office is increasing by five cents to $0.55 from $0.50.Each additional ounce for a First Class Mail letter will cost an extra $0.15 (a decrease from $0.21 in 2018).First Class Mail Flats/Large Envelope rates are not increasing in 2019, remaining at $1.00 (1 oz.), with additional ounces costing $0.15.Postcard rates are also not increasing in 2019, remaining at $0.35.Customers who print postage online (via Stamps.com), the Metered Mail rate will now be a 5 cent discount compared to the Post Office price with rates increasing to $0.50 in 2019 from $0.47 currently.Each additional ounce will cost an extra $0.15 in 2019, a decrease from $0.21 currently.The five cent discount for online postage on a one-ounce First Class Mail letter represents a savings of 9% for consumers and small business owners.